Catalytic hydrocarbon conversion system



Oct. 16, 1945. A. G. OBLAD ETAL 2,337,088

CATALYTIC HYDROCARBON CONVERSION SYSTEM Filed Jan. s1. 1941 www NNN\NWANN Patented ct. 16, 1945 CATALYTIC HYDROCARBON CONVERSION- SYSTEM AlexG. Oblad, Chicago, Ill., and Llewellyn Heard, Hammond, Ind., assignorsto Standard 011 Company, Chicago, Ill., a corporation of Indiana iApplication January 31, 1941, Serial No. 376,820

6 Claims. (Cl. 196-52) This invention relates to a catalytic system forthe conversion of hydrocarbons into high quality motor fuel and itpertains more particularly to a system employing a solid catalyst of atype which is initially highly active but which gradually becomes lessactive due to the deposition thereon of a carbonaceous coating.

Different fractions of crude oil require different treatments foreffecting a conversion thereof into high quality motor fuel. 'Ihe gasfraction may be employed in an alkylation process, it may be cracked ordehydrogenated and polymerized etc. The light naphtha fraction may onlyrequire desulfurization but it may be improved by isomerization,aromatization or reforming. Heavy naphtha may be either thermally orcatalytically reformed or aromatized. Gas oil is preferably subjected tocatalytic cracking. Heavier fractions, suchv as reduced crude, may besubjected to a viscosity breaking conversion for obtaining gas oilcharging stocks or it may be thermally or catalytically cracked. Naphthafrom thermal cracking processes may be markedly improved in octanenumber by catalytic reforming or isoforming processes. An object of ourinvention is to provide a unitary system for effecting a plurality ofthe above processes by means of a single catalyst and to effect at leasttwo of such reactions by said catalyst prior to catalyst regeneration.

Silica-'alumina type catalysts lmay be used for the catalytic crackingof both light and heavy.

petroleum fractions as well as for the desulfurizing and treating ofvarious naphthas. When fresh or regenerated catalyst is used for thecracking of gas oil it exhibits such a high initial activof naphtha orother charging stocks. A furtherobject is to employ a catalyst both forthe treating of naphtha and for the treating of gas oil and i. heavierhydrocarbons in two separate steps before the catalyst is regeneratedfor reuse.

Our invention is applicable to fixed and moving bed systems but it isparticularly applicable in a '35 ity that there is an over-treating, i.e., a decomsystem wherein the catalyst effects the desired conversionwhile it is suspended in reaction vapors and wherein the catalyst isregenerated while suspended in regeneration gases. An important featureof this system is the separation of suspended catalyst from one reactionstream and the suspension of the catalyst in a different reactionvstream prior to the suspension of the catalyst in the regenerationstream. Other objects of the invention will become apparent from thefollowing detailed description. y

In practicing our invention we first deposit sufcient carbonaceousmaterial on the catalyst to inhibit initial superactivity and we thenemploy the conditioned catalyst for effectingvthe desired conversion.For example, we may first contact the catalyst with hydrocarbon gasesatatemperature of about 950 to 1250 F. whereby the gases are partiallycracked and converted into olefins which are particularly suitable forpolymerization, alkylation, gas reversion, or other industrial uses. Thetime of contact with such gases is sufficiently short to preventappreciable carbonaceous deposits but is long enough to deposit a smallamount, preferably about .05 to 1.0% by weight. 'This car.- bonaceousdeposit apparently coats or modifies the superactive catalyst spots andprevents overtreating when the catalyst is subsequently employed foreffecting the desulfurizing or isoformingy of naphtha or for effectingthe cracking of gas oil or heavier hydrocarbons.

Since relatively small amounts of carbonaceous material are deposited onthe catalyst in naphtha treating processes we may effect the initialcatalyst coating' by a naphtha treating process instead of or inaddition to the gas treating processes. A freshly regenerated catalystor a catalyst which already contains a slight carbonaceous nlm may beused for reforming naphtha, isoforming ther-A mally cracked naphtha ordesulfurizing a light or heavy naphtha. In'the naphtha treating processabout 0.05 to 1.0, preferably about 0:1 to 0.5% of carbonaceousmaferialis deposited on the catalyst by a proper selection of temperature, timeof contact, space velocity. etc., so that the quality of the naphtha ismaterially improved at the same time that the catalyst is beingconditioned for the subsequent cracking step. v

Catalyst which has received a light carbonaceous deposit in the gas ornaphtha treating steps is then contacted with gas oil or heavierhydrocarbon vapors at a temperature of about 800 to 1000 F. kand with atime of contact, space velocity, etc., to obtain the desired conversionof these heavy hydrocarbons into high quality motor fuel.

vIlBy preconditioning the catalyst the initial overtreating wlllbeavoided. and there will be a nmarked-improven'ientinproductdistribution, i. e..

-a minimum-degradation to gas and coke. When the 'catalyst hasbecome-relatively spent in the cracking step. itmay be regenerated andreturned to one or more of the preconditioning steps. We prefer toemploy the catalyst for treating naphtha before it is employed forcrackingas 7 oil or heavier hydrocarbons because less carbon isdeposited in the initialsteps of naphtha treating processes than ininitial steps of cracking.

.Also the .naphtha treating processes are usually Vat vhighertemperatures than cracking-so that the catalyst is' employed in agradually' decreasing temperature sequence .from the regeneration stepto the final cracking step. Advantages may be obtainable, however, bytreating naphtha with a catalyst which has become partially spent inconditioning of catalyst by appli/inge light carbonaceous coating onsuperactive catalyst surfaces. A considerable amount of carbonaceousmaterial may remain in the catalystparticles after regeneration due toincomplete combustion in the regeneration step. This residual carbondoes not serve the function of preconditioning the catalyst and is, infact, detrimental. In practicing our invention, we effect regenerationto as complete an extent as is commercially feasible and we then apply alight carbonaceous deposit on the active surfaces of the catalyst beforethe catalyst is employed in'a subsequent treating or cracking step.

The invention will be more fully understood l from the followingdetailed description read in 'conjunction with the accompanying drawingwhich forms a part of this specification and is a schematic flow diagramof a preferred embodiment of our unitary conversion system.

The charging stock to our system may be crude oil or'fraetions thereofIor it maybe a synthetic hydrocarbon prepared Yby a carbonmonoxidehydrogen synthesis or by the hydrogenation of coal. This crudeoil or other charging stock may be heated in a suitable pipe still (notshown) and introduced through line l into crude oil fractionating columnIl. The gas fraction may be withdrawn from the systemfthrough line l2with a particle size ranging from about 200 to 400 mesh. Syntheticcatalysts may be prepared by depositing alumina or other activemetal'oxide either on or in silica gel. Foryinstance, the silicagelmaybe formed in an aluminum salt solution and the resulting gel freed fromacids and alkali metals by boiling withl dilute ammonium hydroxide andwashing. The gel particles may then be crushed, dried and heated toabout 850 to l000 F. Another eiliciet catalyst may be made by ballmilling magnesia with silica gel in the presence of suilicient moistureto form a dcughy mass which may be dried, crushed and heated to atemperature of about 850 to 1000" F. An alumina-silica-zlrconia catalysthas been found to give excellent results in cracking as well as otherconversion processes. Thesilicaalumina, and silica-magnesia catalystsgenerally will be referred to herein as catalysts of the silica-aluminatype and they are characterized by their tendency to become coated withcarbonaceous materials during the course of conversion.

Such catalysts are well known in the art and v require no furtherdetailed description.

The amount of catalyst charged to the gas cracking step may-be theamount later required or all or just the Csi-C4 fraction passed by linesi3 and I4 and pump Ii to coils i6 ofv gas heater pipe still Il. If gasis vented through line I2 a gas from extraneous sources such as a Cs-Csfraction may be introduced through line i8. In the pipe still the gas isheated to a temperature of about 950 to 1250 F., preferably about 110011'., and is then passed through transfer line I9 to reactor 20 foreffecting gas cracking.

Fresh or regenerated powdered catalyst is withdrawn from the base ofstandpipe 2i by a suitable valve or star feeder 2l' and eitherintroduced by line 22 into transfer line i9 or introduced directly intoreactor 20. The catalyst is preferably of the silica-alumina type. Acidtreated bentonite of the type commonly marketed as Super Filtrol may beadvantageously used for this purpose, preferably in powdered form forthe naphtha treating or gas oil cracking steps. The residence time ofthis catalyst in vreactor 20 should be sumciently short to prevent thecarbonaceous deposit from exceeding about 1% and it preferably shouldnot exceed about 0.5% but should be atleast 0.05%. This reactor may,therefore, be of relatively small diameter ascompared with otherreactors in the system and a relatively short contact time and catalystholding time may be provided. Reaction c'onditions at this stage may bevaried to accomplish the desiredconversion of the gaseous hydrocarbonsbut it is preferably carried out under such conditions that only about.05 to 1%, for example about '.2%, of carbonaceousmaterial is depositedon the catalyst (based on weight of catalyst). The vertical velocity ofgas ow through reactor 20 should be upwards of about 1 or 2 feet persecond and the gaseous stream will thus carry the catalyst through line20' to one or more cyolone separators or other separation devices 23from which the cracked gases are vented through line 23 to a suitablealkylation, polymerization,

gas reversion or olefin recovery step.

The coated catalyst falls from separator 23 into hopper 24 and thence tostandpipe 25. The

standpipe may be aerated by an inert gas suchv asV a hydrocabron gas orsteam introduced through-'line 26. Additional aerating gas may beintroduced at the base of the hopper through line 2l. A The aeratinggases may be vented through line` 28 to separation system 23 or line23'.

Naphtha is withdrawn from tower Il through line 29 and it may bewithdrawn from the system through line 30 or. forced by pump 3| throughcoils 32 of naphtha heaterpipe still 33 to transfer line 34 and thencesubjected to desulfurization. Naphtha from other sources may beintroduced into coils 32 from lines 35 'or 36. Thermally cracked naphthais the preferred charge to the naphtha treating step and the treating ofthis charge is called isoforming. This naphtha may be heated in coils 32to temperature of about 800 to 1100 F.. preferably about 900 to 1000 F.,and the transfer line pressure is preferably about atmospheric to about50 pounds per square inch. preferably about l0 or l5 pounds per squareinch. Catalyst from'standpipe 2| may be introduced into this transferline through line 31 or precon ditioned catalyst may be introducedthereto throughvline 88. In other words, we may use the gas cracker 20for preconditioning-catalyst subsequently usedfor naphtha treating or wemay use the naphtha treating step itself for preconditioning catalystfor catalytic cracking. In the latter case reactor 20,`standpipe 25, gasheater Il,

etc., may be entirely dispensed with.

The hot naphtha vapors together with suspended catalyst are introducedat the base of reactor 39 although it should be understood that thecatalyst may be introduced directly intothis reactor instead of withincoming naphtha vapors. Reactor 39 is preferably operated with upwardvertical vapor velocities of about .5 to 5 feet or more per second. Theamount of catalyst in the reactor for eecting isoforming of thermallycracked naphtha may be expressed by the formula where T is tons ofcatalyst in the reactor per hundred barrels of naphtha charged to thereactor per hour, t is catalyst residence time or holding time" in thereactor expressed in minutes and a is a constant which may range fromabout 0.005 to 0.05, preferably 0.02. The time of oil contact in thereactor may range from about 2 to 40 or more seconds. The size andcross-sectional area of the reactor should be of sufcient magnitude sothat the vertical vapor velocity therein will re sult in a catalystdensity which-will give the approximate amount of catalyst in thereactor indicated by the above formula. Catalyst is withdrawn from thereactor at substantially the same rate as it is introduced thereto andthe treated naphtha vapors together with this withdrawn catalyst areintroduced by line d@ into one or more cyclone separators or equivalentseparation means di from which vapors are removed through line t2 andline i3 to a separate fractionator system or through line [lil to thefractionator for catalytic conversion products.

The catalyst' falls from separator di to hopper it and thence tostandpipe 56. Aerating gas is introduced through lines fil and :it andmay bel ture of about S to 10.50 F., preferably about 925 to 950 F. anda transfer line pressure oi? about atmospheric to about 50 pounds persquare inch, preferably about l0 to i5 pounds per square inch. Transferline ti" introduces these hot gas oil vapors to the base of reactor t.Catalyst from standpipe dt is either introduced into the transfer line5"] through line 59 or is introduced directly into the base of reactor58. The weight ratio of catalyst-to-oi1 introduced into one reactor mayvary from about .1:1 to 10:1 but is preferably about 3:1.

The amount of catalyst which is maintained in catalyst reactor tit isrepresented by the formula; hereinabove stated:

T=at-sac but in this case the constant c ranges from .3 to

3.0 and is preferably about 1.2 although with weak catalysts andrefractive stocks,l etc., it may be .necessary to go up as high as 6 or-even 12.

T is tons of catalyst per hundred barrels of gas oil feed per hourcharged to the reactor and i is catalyst residence time in minutes.Reactor 58 is designed with suillcient cross-sectional area to give avertical vapor velocity of about .5 to 5, preferably about 1.5 to 2 feetper second which will result in a catalyst density of about 1 to 35,preferably about 10 to 20 pounds per cubic foot. The residence time ofthe gas oil vapors in the reactor may range rfrom a few seconds to oneor more minutes, preferably about 2 to 40 seconds.

Reaction products and spent catalyst are withdrawn from the top ofreactor 58 through line S0 and introduced into one or more cycloneseparators or other suitable separation means 6i from the top of whichreaction products are withdrawn through line t2 to a fractionatingsystem dia-` grammatically represented by column t3.

Spent catalyst drops from separator ti to spent catalyst hopper andstripper td. thence to standpipe e5. Aerating gas is introduced throughline @t and stripping gas through line tl, these gases being removedfrom the top of the hopper through line t8 and either returned to theseparating means Si or introduced into line t2.

Spent catalyst from the base of standpipe dit is discharged through linet9, piclred up by air introduced through line 'it and introduced throughline lll to the base oi regenerator l2 although here again it should beunderstood that the air or oxygen-containing gas may be introduceddirectly at the base of the regenerator andthe spent catalyst may beinjected directly into the regenerator by any suitable means. The

regenerator may be a large cylindrical vessel with a conical bottom, aVessel of the same type as reactors t@ and be. For a dense phaseregeneration the regenerator should have suiiicient cross-sectional areato provide a vertical gas velocity therein of about .5 to 5, preferablyabout 1/2 feet' per second. The regeneratoi'V silica-alumina catalystthis temperature is usu ally about 1050 to llililf F. or lower.

Regeneration gases with suspended regelaar ated catalyst are withdrawnfrom the top of re generator it through line 'it and introduced into oneor more cyclone separators or other suitable separation means l5 fromwhich the regeneran tion gases are vented through line 'iii to suitableheat recovery means such as waste heat boiler, turbines or the like.

Hot regenerated catalyst preferably at a temperature of about 1000 F.fallsirom separator 'i5 into hopper lll and thence to standpipe 2i. A

hot aerating gas is introduced through lines it and it. Such gases areremoved through line Si@ either to the separation system 'i5 or to lineit.

The residue or liquid fraction from the base of iractionating tower ilis withdrawn through line di and either removed from the system throughline 82 or forced by pump te through coils td of reduced crude pipestill t5; Reduced crude or heavy charging stocks may lbe intro line 86and a refractory. gas oil may be introduced throughiine 81. The heavynaphtha fraction withdrawn from tower through line 80 may be introducedthrough line 89 to coils 84 or 'may be passed through line 90 toseparate coils 9| in the reduced crude pipe still or independent heater.When separate coils are used the material discharged from coils 84 maybe of a temperature of about 850 to 1050o F., preferably about 905" F.and the vapors discharged from coils 9| may be of a temperature of about900 to 1100 F., preferably about 1000 F. These streams are introduced bytransfer lines 92 to coke drum or evaporator 93 from the base of whichcoke or tar maybe withdrawn through the base of the drum or line 94.Overhead products from the coke drum or evaporator are withdrawn through1ine 95 to bubble tower 96 from the base of which a refractory gas oilis withdrawn through line 91 and returned by line 81 to coils 84. Ifdesired a light gas oil fraction (e. g. about 600` F. to 650 F. endpoint) may be withdrawn through line 56 to coils 53 `of gas oil heater54. The gasoline fraction may be withdrawn through line 91' fortreating, blending or storage or it may be withdrawn through line 36 tonaphtha heating coils 32 and thence charged to reactor 39 forisoforming. Coke still naphtha is an excellent isoforming chargingstock. The gas withdrawn through line 98 may be charged to analkylation, polymerization, gas reversion or other external process.

If desired the overhead from the evaporator may be introduced throughline 99 to fractionating column 63. Gasoline from this column may bewithdrawn through line for further treating, blending or storage. Gasesmay be withdrawn through line |0| for use: in other processes or it maybe passed through line |02 to line 4 and coils I6 of gas heater i1. Thecycle gas oil from the base of column 53 may be withdrawn from thesystem through line |03 or recycled through line |04 and line 81 tocoils 84 of the thermal pipe still 85 or passed through separate coilsand fractionating systems to produce isoformable charging stocks.

In the preferred embodiment of the invention hereinabove described thehot regenerated catalyst was first conditioned by contact with ahydrocarbon gas, then used for the treating of naphtha and then for thecracking of gas oil. In such a process the gas contacting step might beat a temperature of about 1000 to l050 F., the naphtha treating at atemperature of about 950 F.- and the cracking at a temperature of about900 F. The gas contacting step may, however, be omitted and the catalystmay simply vbe employed for treating naphtha and gas oil respectively.Certain advantages may be obtained by utilizing the catalyst forcracking prior to its use for naphtha treating because a catalyst whichhas ceased to give a desirable product distribution in cracking maystill have considerable utility for effecting the isoforming ofthermally cracked naphtha. If the process were to be operated in thismanner transfer line 51 would discharge through line |05 and transferline 34 through line |06.

In the preferred example hereinabove described each of the catalystcontacting steps is effected while the catalyst is in gas or vaporsuspension. Furthermore, the catalyst is maintained in uent conditionthroughout the entire system, an aerating gas velocity of about .05 to.5

duced from other extraneous sources through feet per second beingmaintained in the various columns and hoppers for this purpose. Thepurpose of the columns is to provide the necessary pressure at variouspoints in the system and the catalyst is carried from the base of onecolumn to the top of the other column by the pneumatic gas lift effectof the reaction vapors or regeneration gases. It should be understood,however, that our invention is not limited to systems of the so-calledfluid type as hereinabove described but is likewise applicable to movingbed catalyst systems or even to fixed bed systems.

The outstanding feature of our invention is the preconditioning of thecatalyst in one reaction so that optimum catalyst activity may beobtained in another reaction without the detriment of hyper-activity andover-treating. As above stated, the small amount of carbon which isdeposited on superactive catalyst surfaces is beneficial for naphthatreating or gas oil cracking while the carbonaceous material which isincompletely burned from the catalyst in the regenerator is actuallydetrimental in that it impairs catalyst activity and leads toundesirable product distribution.

i Our invention is not limited to the particular modification nor to theparticular details hereinabove set forth and many other modificationsand operating conditions will be apparent to those skilled in the artfrom the above description.

One modication whichdeserves special mention is that of employing aparallel arrangement of preconditioning contacting steps prior to acatalytic cracking step so that a part of the catalyst receives-itssmalldeposit of carbonaceous material by contacting gases and another part ofthe catalyst receives its initial carbonaceous coating by contactingnaphtha vapors. The invention is applicable to any and all arrangementsfor effecting the deposit of about .05 to 1.0% measured as carbon on thecatalyst by use of a relatively clean stock such as a naphtha or ahydrocarbon gas. If the catalyst is initially contacted with a dirtystock such as a tar or refractory cycle stock, the advantages of ourprocess are not obtained because an undesirable carbonaceous coating islaid down on the catalyst which may impair its subsequent activity andgive undesirable product distribution in a subsequen conversion. Y

We claim:

1. The method of obtaining high yields of high quality motor fuel andlow losses to gas and coke in a catalytic conversion process whereinhydrocarbon vapors are contacted with a catalyst comrprising silica anda metal oxide' of the class consisting of alumina and magnesia whichmethod comprises initially contacting said catalyst at elevatedtemperatures with clean hydrocarbon vapors under such conditions as todeposit on said catalyst about .05 to 1.0% by weight of carbonaceousmaterial, separating said vapors' from said catalyst under conditionsfor preventing condensation of vapors to liquids whereby the catalyst ismaintained in dry condition, and subsequently contacting a moving massof said catalyst with gas oil vapors at a temperature of about 800 to1000 F., at a pressure of about atmospheric to 50 pounds per squareinch, with a gas oil vapor residence time in the subsequent contactingZone of at least 2 to 40 seconds and with an amount of catalyst dened bythe following formula:

T=atj34 where T is tons of catalyst in the subsequent contacting zoneper hundred barrels of charging stock per hour, t is catalyst residencetime in minutes and a is a 0.3 to 12.0.

2. The method of claim 1 wherein the gas oil contacting step is effectedwhile the catalyst is in vapor suspension and the catalyst density insuch suspension is about 1 to 35 pounds per cubic foot.

3. The method of claim 1 wherein the gas oil constant ranging from aboutI contacting step is eiected while the catalyst is in v vapor suspensionand wherein the vertical velocity of the gas oil vapors in thecontacting step ranges from about .5 to 5 feet per second.

4. The method of utilizing a silica-alumina catalyst both for thetreatmentv ofnaphtha and gas oil respectively which comprises firstsuspend# ing catalyst in naphtha vapors under such conditions oftemperature, pressure and contacting time that a carbonaceous deposit ofabout .05

to 1.0% by weight is deposited thereon, separating gases and vapors fromthe catalyst under such conditions as to leave the catalyst insubstandry uent form, suspending the dry iiuent tially cata yst in gasoil lvapors and contacting the 6. The method ofobtaining high yields ofhigh quality motor fuel and low losses to gas and coke in .a catalyticconversion process wherein hydrocarbon vapors are contacted with -acatalyst comprising silica and a metal oxide of the class consisting ofalumina and magnesia, which method comprises initially treating saidcatalyst at an elevated temperature with a rst stream of hot hydrocarbonvapors under such conditions as to deposit on said catalyst about 0.05to 1% by weight of carbonaceous material, separating said vapors fromsaid catalystr under conditions for preventing condensation of vapors toliquids whereby the catalyst is maintained in hot, dry condition,passing said separated catalyst downwardly through a substantiallyvertical zone of lsaid stream, introducing said stream of suspendedcatalyst at the base of a-contacting zone of large cross-sectional area,passing vapors up wardly through said contacting zone at a verticalvelocity within the approximate range of .5 to 5 feet per second andsuilicient to maintain therein a catalyst suspension having a densitywithin the approximate range of 10 to- 35 pounds per cubic foot, andeffecting contact of catalyst with vapors in said contacting zone at atemperature within the approximate range of 800 to 1000 F., at apressure-cf about atmospheric to about 50 pounds per square inch andwith a vapor i'sidence time in the contacting zone of at least 2 to 40seconds.

, ALEX G. OBLAD.

LLEWELLYN HEARD.

